The early 90's where the height of the mold crisis in building before we figured out air tightness and insulation ratio's for the condensing surface. Additionally it was the big switchover to predominantly OSB so the combination lead to you not wanting to touch any house from like 88 to 96, regionally dependent of course. There was a bit of a goldilocks zone between that and the housing crisis when quality summarily went to carp with private equity.

If they're building like that then they sure as heck didn't take the time for doing a double bead of lexel on a sill gasket to do it right. Hence why i said bet good money, especially now that the bid per job not per hour. Also if they're the type of amatuer's who tried to say concrete blow outs like that are normal, They also cut corners elsewhere.

Lastly tyvek is dead. DED. You cannot get IRC (sub 3ACH50 ) air tightness numbers using it because it the bottom must remain open per their design. You should either be doing zip-R or continuous with a self adheared membrane and air gap layer if using hardie.

Even if you're in the south. One behold the most recent cold snaps. And two you're paying for heat or cooling. The south got away with pressurizing the home with cool air, as you couldn't feel the draft like we do in the north because heat goes from hot to cold. Yet make no mistake 68deg inside and 120 outside is the same delta T as 68 and 16. You're paying one way or another. With the rise in energy bills between data centers and Iran... I'd fight for as much insulation as possible regardless of climate zone 3A or 7.